The invention relates to process for the operation of a bulk-material regenerator or regenerator according to the preamble of claim 1. It also relates to a regenerator according to the preamble of claim 6.
Such regenerators are used for heating gases to temperatures of customarily 800xc2x0 C. In the operation of blast furnaces, for example, regenerators serve for generating a hot blast of air at a temperature of 1200xc2x0 C. Such regenerators are known, for example, from U.S. Pat. No. 2,272,108, DE 41 08 744 C1 or DE 42 38 652 C1.
In the case of the known regenerators, a bulk material is received in an annular space between an inner cylindrically designed so-called hot grid and a so-called cold grid coaxially surrounding the latter. Both the hot grid and the cold grid are provided with apertures or openings, the diameter of which is chosen such that a passing-through of gas is possible, but a passing-through of bulk material is impossible. In practice, the cold grid is customarily produced from a perforated metal plate and the hot grid is customarily produced from ceramic materials, for example from fireclay bricks. Gravel or aluminum oxide beads are used, for example, as bulk material.
In the case of the known apparatus, the hot grid and/or cold grid disadvantageously ruptures after only short operating times or service lives. The replacement of a ruptured hot grid and/or cold grid is very costly.
The object of the invention is to specify a process for the operation of a regenerator and a regenerator which ensure an improved service life.
This object is achieved by the features of claims 1 and 6. Expedient refinements emerge from the features of claims 2 to 5 and 7 to 18.
According to what is specified by the invention with respect to the process, it is provided that a predetermined amount of bulk material is discharged during or after the passing-through of hot gas, so that a compressive stress exerted by the bulk material on the hot grid or cold grid is reduced.xe2x80x94The service life of the regenerator is drastically prolonged as a result.
The discharged bulk material is advantageously fed back into the annular space. As a result, the required minimum filling level of bulk material is maintained. If bulk material of high value is used, the reuse may have the effect of reducing operating costs.
The discharged bulk material may be transported pneumatically, it advantageously being fed to the annular space through a feed opening provided in the vicinity of its top. In this case, a transporting gas can be separated from the bulk material and be blown off into the surroundings. The aforementioned features make it possible for the process to be automated.
According to what is specified by the invention with respect to the regenerator, it is provided that the hot grid and/or cold grid is/are designed such that the bulk material can freely expand radially during heating up.xe2x80x94Consequently, the effect of thermally induced compressive stresses of the bulk material on the hot grid and/or cold grid is reduced. A rupture of the hot grid and/or cold grid is avoided. The service life of the regenerator is prolonged.
According to one refining feature, the hot grid and/or cold grid is provided with at least one opening, the diameter of which is greater than the maximum particle diameter, so that compressive stress formed in the bulk material can be compensated by a proportion of the bulk material passing through the opening. A device for catching bulk material emerging from the opening is expediently provided on the side of the opening facing away from the annular space.
According to a further refining feature, the device for catching has at least one sloping surface running obliquely with respect to the axis of the regenerator, the sloping surface running from the outer side of the hot grid or cold grid, facing away from the annular space, to an inner side, facing toward the annular space, and declining in the direction of the bottom of the annular space.
Furthermore, the apparatus may be closable by means of a cover provided with apertures, the apertures being formed such that a passing-through of gas is possible, but a passing-through of bulk material is impossible. An entrainment of individual particles of bulk material by the emerging stream of gas is avoided as a result.
According to a further refinement, at least one discharge opening is provided in the bottom of the annular space. Discharging bulk material during or after heating up likewise makes it possible to reduce compressive stresses exerted by the bulk material on the hot grid and/or cold grid.
The discharge opening expediently opens into a tube, it being possible to provide a means for closing the tube. The tube advantageously opens into a transporting tube. A device for generating a stream of transporting gas may be connected to the transporting tube, so that the bulk material can be transported pneumatically through the transporting tube. The aforementioned features make possible an automated return of discharged bulk material into the annular space.
The transporting tube may be in connection with a feed opening provided in the vicinity of the top of the annular space. A device for separating the bulk material from the transporting gas is advantageously provided on the side of the feed opening facing away from the annular space. Cooling down in the region of the annular space is avoided as a result.